1. Field of the Invention
The present invention relates to a process for manufacturing an alkenylaromatic compound which is an industrially valuable compound as a raw material for the manufacture of naphthalenedicarboxylic acid, a highly useful raw material of polymers such as polyethylene naphthalate (PEN).
2. Description of the Background Art
In the process for manufacturing alkenyl aromatic compounds, an alkylbenzene and 1,3-butadiene are reacted in the presence of an alkali metal as a catalyst. Conventionally known catalysts used in this reaction are metallic potassium (Japanese Patent Publication (kokoku) No. 17973/1975) and a combination of metallic potassium and metallic sodium (Japanese Patent Publication (kokoku) Nos. 34570/1981, 26489/1982, and 17973/1975).
Conventional methods using these catalysts, however, have the following drawbacks.
(1) High production cost due to the use of expensive metallic potassium. PA1 (2) Risks associated with the use of metallic potassium. Metallic potassium is highly reactive with water, moist air, and the like, and is thus ignited by merely brought to come into contact with them. Thus, it may fire combustible materials, such as raw materials and reaction products. Therefore, using metallic potassium as it is is very dangerous. PA1 (a) metallic sodium, PA1 (b) at least one compound selected from the group consisting of salts of potassium, salts of rubidium, and salts of an alkaline earth metal, and PA1 (c) an aromatic compound capable of producing a charge-transfer complex together with metallic sodium.
In an effort of avoiding the use of metallic potassium, a method of using metallic sodium and an inorganic salt of potassium has been proposed (Japanese Patent Laid-open (kokai) Nos. 31935/1972, 226927/1992, and WO 91-16284).
This method does not necessarily provide industrial advantage, because of (3) requirement for special agitators, such as an emulsification apparatus, and for the use of high purity inorganic salt of potassium.
An object of the present invention is therefore to provide a process for manufacturing an alkenyl aromatic compound from an alkylbenzene and 1,3-butadiene, which is free from all the problems (1)-(3) above.
As a result of extensive studies for achieving this object, the present inventor has found that the combined use of (a) metallic sodium, (b) a salt of potassium, rubidium, or an alkaline earth metal, in place of metallic potassium, and (c) an aromatic compound capable of producing a charge-transfer complex together with metallic sodium ensures reducing the amount of metallic sodium and increasing the yield of the alkenyl aromatic compound by the reaction of alkylbenzene and 1,3-butadiene by using only a simple agitator.